There are many races of this slender, long-tailed colobus, with coloration ranging from orange-red to reddish-brown, often with black on the back and shoulders. The underparts are reddish-yellow to gray or white. Females are smaller than males, but otherwise look similar.

The red colobus monkey lives in a troop of 50 to 100 animals made up of many small family groups, each comprising a male and several females and their young. The colobus troops are active during the day, when they feed among the branches on flowers, shoots, fruit and leaves, leaping acrobatically from tree to tree.

The female produces 1 young after a gestation period of between 4 and 5 1/4 months. She nurses the infant until it is ready to be weaned at between 9 and 12 months.

Western Red Colobus

The western red colobus is one of the leaf monkeys. Like other red colobus monkeys and their relatives the langurs, this species survives by eating leaves or, more specifically in the western red colobus’s case, the petiole, or leaf stalk.

Plant food does not contain very many nutrients, so colobus monkeys must eat a lot to sustain them. Plant food is also very hard to digest efficiently; most of a leaf is made up of a tough fibrous substance called cellulose. Although cellulose is made up of chains of sugars molecules, it cannot be digested by a normal monkey. For this reason, red colobus monkeys has a stomach split into four chambers (similar to that of a cow). The different stomach chambers contain bacteria that can break down cellulose fibres into an acidic sugary soup, which the monkeys can then digest themselves. This type of digestion takes a very long time, and so western red colobus monkeys often spend long periods sitting with full stomachs. (The process also produces a lot of gas, so the monkeys often look bloated.)

The western red colobus monkeys has a very short, almost useless, thumb and four very long fingers, which it hooks over branches so that it can swing through the trees.

Having to sit still all the time, western red colobus monkeys are easy to hunt. Human hunters have nearly wiped them out in some places, but they are also the favourite prey of another ape - the chimpanzee.

Distribution: West Africa.

Habitat: Rainforest, woodlands and savannah.

Food: Leaves.

Size: 45 - 67 cm (17.75 - 26.5 in); 5 - 11 kg (11 - 24.25 lb).

Maturity: Unknown.

Breeding: Single young born to each female every 2 years. Females mate with several males when on heat. The exact gestation period is uncertain but is probably about 100 days.

Life span: 20 years.

Status: Critically endangered.

Tana River Red Colobus

Size: 45 - 67 cm (17.75 - 26.5 in); 5.8 kg (12.75 lb).

This critically endangered species of red colobus monkey lives in the forests around the Tana River, which flows from the Kenyan Highlands to the Indian Ocean. Flooding from the river supports a tropical forest in a wider region dominated by savannahs. Nevertheless, the Tana River forest is considerably drier than the habitats of other red colobus monkeys. This forces the species to be less reliant on leaves than other colobus; in fact, less than half the monkey's diet is made up of leaves. The rest comprises fruits, seeds, buds and flowers. Living in the isolation of the Tana River Valley, this red colobus monkeys is not threatened by predators in the same way as more common colobuses. As a result, members of this species are less likely to work together to fend off threats.